Definition: Process by which new species evolve from ancestral species
Requirements:
A permanent barrier to breeding between members of the same species (Isolation)
Types of barriers:
Geographic isolation
Physical barrier separates a population into groups
Ex. River, mountain range, ocean, volcano, etc.
Reproductive Isolation
Occurs when members of the same species are prevented from producing fertile offspring
Ex. Different mating seasons, differing flowering times, polyploidy (type of mutation—plants get extra sets of chromosomes, sometimes many extra sets, they can’t reproduce with a normal member of its species.
Rate of Evolution
Gradualism:
Evolution or speciation occurs slowly and steadily over millions of years (slow and steady change over time)
Punctuated Equilibrium:
Species stay the same unless there is some type of pressure to change. When environmental changes exert pressure, change occurs rapidly.
Fossil evidence supports both types.
Patterns of Evolution
Divergent Evolution
Related species become less alike
Adaptive Radiation
Members of the same species adapt to a variety of environmental conditions and radiate out into separate species through divergent evolution and isolation
Darwin’s Finches
Convergent Evolution
Unrelated species become more similar--occurs when unrelated species adapt to similar environments
ex. sharks and dolphins; bats and butterflies; american cacti and african euphorbs
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Population Genetics
Speciation (Download Copy)
Definition: Process by which new species evolve from ancestral species
Requirements:
A permanent barrier to breeding between members of the same species (Isolation)
Types of barriers:
Geographic isolation
Physical barrier separates a population into groups
Ex. River, mountain range, ocean, volcano, etc.
Reproductive Isolation
Occurs when members of the same species are prevented from producing fertile offspring
Ex. Different mating seasons, differing flowering times, polyploidy (type of mutation—plants get extra sets of chromosomes, sometimes many extra sets, they can’t reproduce with a normal member of its species.
Rate of Evolution
Gradualism:
Evolution or speciation occurs slowly and steadily over millions of years (slow and steady change over time)
Punctuated Equilibrium:
Species stay the same unless there is some type of pressure to change. When environmental changes exert pressure, change occurs rapidly.
Fossil evidence supports both types.
Patterns of Evolution
Divergent Evolution
Related species become less alike
Adaptive Radiation
Members of the same species adapt to a variety of environmental conditions and radiate out into separate species through divergent evolution and isolation
Convergent Evolution
Unrelated species become more similar--occurs when unrelated species adapt to similar environments
ex. sharks and dolphins; bats and butterflies; american cacti and african euphorbs